Steel slabs commonly are conditioned by moving scarfing units along the top, bottom, and side surfaces of a steel slab to eliminate surface defects such as cracks, seams, and slag inclusions. One conventional scarfing apparatus includes top, bottom, and opposite side scarfing units that are mounted across the width and end portions of a support, to concurrently scarf all sides of the slab as the slab is passed therebetween.
The top, side, and bottom scarfing units all include a manifold and head assembly, which receives and distributes oxygen and fuel gas to upper and lower preheat blocks. The upper and lower preheat blocks are spaced from each other to define between the two blocks an oxygen scarfing slot through which a quantity of oxygen is blown onto the slab surface to enable scarfing. The lower preheat block includes a fuel gas channel having a discharge opening positioned adjacent to the oxygen slot for discharging a fuel gas adjacent to the oxygen flow, for the purpose of maintaining the oxidation reaction on the surface of the workpiece. As illustrated for example in U.S. Pat. No. 2,838,431, the lower preheat block typically is a one-piece unit, and includes a row of separate fuel gas outlet ports extending across the width of the front face. The fuel gas is delivered to the ports through a number of laterally spaced apart fuel gas lines which extend from the rear face of the block to a transverse internal bore which is positioned just behind and in communication with the inner ends of the outlet ports. A divider bar, comprising a rod with a number of spaced apart O-ring seals, is positioned in the transverse bore so as to divide the fuel gas bore into uniform chambers. The ends of the transverse bore are closed with end seals.
As will be apparent, the components of the gas delivery system of the conventional lower block are difficult to fabricate and maintain, which adds to the expense and operating complexity of the system.
It has been previously proposed to use a continuous outlet slot for the fuel gas in the lower block, as opposed to the row of separate fuel gas outlet ports, note for example at the Jones et al., U.S. Pat. No. 2,356,197 at 49a, and the patent to Fuhrhop, U.S. Pat. No. 4,115,154 at column 6, lines 41-44. However, it is not believed that a continuous slot of this type has been adopted commercially, apparently because of the difficulty of achieving a uniform discharge of the gas along the length of the slot.
It is accordingly an object of the present invention to provide a lower block assembly for a thermochemical scarfing apparatus, which includes an efficient and simple gas delivery system for delivering a stream of fuel gas uniformly across the full width of the metal workpiece.
It is also an object of the present invention to provide a lower block assembly for a metal scarfing apparatus which achieves a more smooth scarfed surface on the workpiece.